1. Field of the Invention
The present invention relates to an underwater robot based on flapping, which includes an actuator prepared with a smart material and directional material.
2. Discussion of the Related Art
Through recent studies, smart materials are widely used for various problems related with an active or passive control of structure. The material may be shape memory alloy. The smart materials may be directly attached to the structure, or may be inserted into another material to be used as an actuator.
Among the various smart materials, researches for preparing a shape memory alloy embedded composite may be as follows: Roger (Craig A. Rogers, “Active vibration and structural acoustic control of shape memory alloy hybrid composites: Experimental results,” The Journal of the Acoustical Society of America, Vol. 88, No. 6, pp. 2803-2811, 1990); Baz (A. Baz, T. Chen, and J. Ro, “Shape control of NITINOL-reinforced composite beams,” Composites: Part B, Vol. 31, pp. 631-642, 2000); Jung (B. S, Jung, M. S. Kim, Y. M. Kim, W. Y. Lee, and S. H. Ahn, “Fabrication of smart air intake structure using Shape Memory Alloy wire embedded composite,” Physica Scripta, accepted, 2010); and Villanueva (A. A. Villanueva, K. B. Joshi, J. B. Blottmanm, and S. Priya, “A bio-inspired shape memory alloy composite (BISMAC) actuator,” Smart Materials and Structure, Vol. 19, pp. 1-17, 2010).
There are researches for studying a small-sized robot using the shape memory alloy, for example, Kim (B. K Kim, M. G Lee, Y. P Lee, Y. I Kim and G. H Lee, “An earthworm-like micro robot using shape memory alloy actuator”, Sensors and Actuators A 125 (2006) 429437); Koh (J. S Koh and K. J Cho, “Omegabot: Biominetic Inchworm Robot using SMA Coil Actuator and Smart Composite Microstructures (SCM)”, International Conference on Robotics and Biominetics, Dec. 19-23, 2009, Guilin, China); and Kim (M. S. Kim, W. S. Chu, J. H. Lee, Y. M. Kim, B. S. Jung and S. H. Ahn, “Manufacturing of inchworm robot using Shape Memory Alloy (SMA) embedded composite structure,” International Journal of Precision Engineering and Manufacturing, accepted, 2011).
Other smart structures may be multi-stable complex structures, and shape memory alloy composites.
The multi-stable complex structures may be a bi-stable morphing airfoil proposed by Diaconu (Diaconu, C. G., Weaver, P. M., Mattioni, F., Concepts for morphing airfoil sections using bi-stable laminated composite structures, Thin-Walled Structures 46 (6), pp. 689-701, 2008), and a multi-stable morphing wing proposed by Iannucci (L. Iannucci and A. Fontanazza, Design of Morphing Wing Structures, 3rd SEAS DTC Technical Conference, Edinburgh, 2008). These multi-stable complex structures are maintained in the deformed state without additional energy. However, these multi-stable complex structures are disadvantageous in that they can be deformed only in the designed shape, that is, it is difficult to change the structures to the various desired shapes.
The shape memory alloy embedded composites are most generally known as the smart structure, which have been actively studied by Lagoudas et al. 1994, Kawai et al. 1999, Murasawa et al. 2004, Khalili et al. 2007a, b, Yongsheng and Shuangshuang 2007, Zhou et al. 2004, Dano and Hyer 2003, and etc. These kinds of smart structure can be controlled to be deformed in the desired shape, but it needs additional energy. The aforementioned smart structures are limited only to hard matrix.
As mentioned above, the smart materials are widely used for various problems related with the active or passive control of structure.
However, even though the various results, deformation in most of the structures using the smart material is limited to linear deformation or out-of-plane bending deformation, and the degree of deformation is too low, thereby causing the limited utilization. Also, since the actuator occupies too large space in the entire structure, it is difficult to obtain a small-sized structure.
Furthermore, it needs a complicated structure for realizing the smooth and continuous motion (for example, the increased number of motors, and the increased number of joints).